Methodology for diagnosing motor issue - 749 - Page 2 - Ducati.ms - The Ultimate Ducati Forum
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post #11 of 22 (permalink) Old May 7th, 2019, 11:22 am Thread Starter
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One more video for funsies (and to get my post count to 30!). This time with no clutch and no plugs.
Maybe there is some knocking detectable with the plugs installed and the motor making compression? IDK. Compression test is next, just need to get a hold of a tester.

Is it ok to run the engine without the clutch pack installed?

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post #12 of 22 (permalink) Old May 7th, 2019, 2:10 pm
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You probably won’t hear any ‘knocking’ until there is combustion pressure on the piston. If you 100% saw copper material on the plug magnet, then you can be sure it’s rod bearing related aim which case a tear down is needed.

If not, and judging by sound alone, I’d put oil in it and run it. Compression and leakdown testing will not point to a rod bearing failure unless the failure is so bad youd would’ve already known otherwise.


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post #13 of 22 (permalink) Old May 7th, 2019, 2:42 pm Thread Starter
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Noted, thanks. No copper on the plug magnet but isn't copper non-magnetic? A few tiny slivers in the oil screen. Still haven't split the filter open.
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post #14 of 22 (permalink) Old May 7th, 2019, 4:58 pm
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I will wager my .02$ on a main bearing failure.

Though my 749 motor had a broken rod when it appears a rod bolt fell out. the rest was destroyed by the owner finishing the lap.
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post #15 of 22 (permalink) Old May 7th, 2019, 7:51 pm Thread Starter
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I will wager my .02$ on a main bearing failure.

Though my 749 motor had a broken rod when it appears a rod bolt fell out. the rest was destroyed by the owner finishing the lap.
Well, I did as Nismo suggested earlier and attached the crank turning tool and spun by hand with the plugs out. It didn't feel gritty, but maybe I could feel some slight rhythmic bumpiness of a bad bearing? Really hard to say it was very subtle.
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post #16 of 22 (permalink) Old May 7th, 2019, 8:16 pm
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Noted, thanks. No copper on the plug magnet but isn't copper non-magnetic? A few tiny slivers in the oil screen. Still haven't split the filter open.


Copper is non ferrous, but so is aluminum. If you felt no play at all in the rod bearings via pushing down on a piston just past TDC, and there’s no copper at all in the screen or filter, I’d wager there’s no rod bearings failure. Wear? Sure, but failure? No.


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post #17 of 22 (permalink) Old May 7th, 2019, 9:00 pm
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Not rod bearings but MAIN bearings, no copper there and you could not feel them by turning over the motor. If you pull the alternator cover and clutch cover and then remove the gears on the crank so that all you have is a crankshaft you then can often feel a bad main.

Before getting that far in you check everything along the way like the small bearing in the alternator cover. I just had a 1200 last year that had that bearing failure. go in slow and with eyes open that is steel to be on the magnet.
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post #18 of 22 (permalink) Old May 7th, 2019, 9:04 pm
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that much fur on the magnet would be mains, loose flywheel nut or starter clutch ime.
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know all wanker
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post #19 of 22 (permalink) Old May 8th, 2019, 10:40 am Thread Starter
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Thanks all. This is quite the fun learning experience, and I'm going deeper into motor issues than I have in the past. It's also a great excuse to buy new tools. I'll keep posting what I find. Maybe it won't be so bad?

Who am I kidding! Lol.

It's just crazy to think that a motor with 4k on it would be toast.
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post #20 of 22 (permalink) Old May 10th, 2019, 9:15 am Thread Starter
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Fuel pump is not cooperating, but I chanced a squirt of starting fluid down the intake runners. Clutch completely removed to eliminate the clankety clank. It sure sounds ok…

Getting it idling for more than 10 seconds on gas will be the real tell.


Got to talking with the PO, and he described the event as going into a tight right hander and instead of the slipper clutch engaging (not sure which brand he has on it) the motor caught the revs on decel, sounded knocky\pingy and wouldn't accelerate. He immediately pulled off and didn't attempt to start again. What would a slipper clutch do (sorry don't have much experience with them) if the fuel pump died mid engagement? Running super lean\starving for gas could explain maybe the weird engine noises?
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